Such step-action indexing mechanisms e.g. configured in accordance with GB 1317315, are used in particular in medical aerosol therapy for the treatment of respiratory conditions. A pressurized cartridge located in the unit contains the medicament which is to be inhaled. In order for the latter to be expelled, it is necessary for the cartridge to be displaced axially in the unit. The unit, which usually more or less fully encloses the cartridge, also conventionally has a mouthpiece and/or an adapter for inhaling through the nose. It is necessary to provide the user with a counter for indicating the quantity of medicament which has been used or is still present in the cartridge. Since a defined quantity of medicament is discharged upon each cartridge actuation, it is known for the medicament is discharged upon each cartridge actuation, it is known for the counter to be coupled to the axial displacement of the cartridge in the inhaler housing for the purpose of discharging medicaments. The generically determined solution, which is known for this purpose, is too large to be accommodated in normal units. Moreover, it is difficult to assemble, in particular in respect of the step-action indexing fingers, which are mounted on transverse pins in relation to the step-action indexing-mechanism housing and are to be loaded by separate springs. The counting accuracy which can be achieved is insufficient for use with medicaments. Upon insertion or removal, e.g. for cleaning purposes, incorrect counting can easily take place such that the step-action counter counts a step which did not actually constitute a dispensing step in the inhaler.
An inhaler appliance is known from EP 480488 with an upper cap which is displaceable in the direction of a cartridge, which cap surrounds an annular part from which there extend obliquely, oppositely-directed resilient step-action indexing fingers, the ends of which engage in a toothed rim, when the cap is pushed in the direction of the cartridge, so that the linear displacement of the cap is converted into a rotational movement of a scale ring. The rotation of the scale ring is visible through a window provided on the cap. The solution is costly and is in particular very disadvantageous in respect of cleanability.
It is also the case elsewhere that there is a need for straightforwardly constructed counters which operate independently.
In respect of the above described prior art, a technical problem addressed by the invention is considered as that of configuring a step-action indexing mechanism of the type in question in a spatially advantageous manner, along with simplified construction, such that it is more reliable to handle.